1. Field of the Invention
This invention relates to multicolor optical circuits for performing logical operations.
2. Description of the Prior Art
Logic circuits are designed to perform predetermined logical operations usually governed by the principles of Boolean algebra. Logic gates for performing Boolean logical operations AND, OR, NAND, NOR and NOT are commercially available and extensively used. Also well known are logic gates for performing diverse logical operations based on a majority or a minority concept.
It will be recalled that an OR gate provides an output low level signal when all its inputs are at a low level and an output high level signal when at least one of its inputs is at a high level. The output, however, is not capable of indicating which ones, or how many, of its inputs are at a high level.
In a similar fashion, an AND gate provides an output high level signal when all its inputs are at a high level and an output low level signal when at least one of its inputs is at a low level, without indicating which ones, or how many, of its inputs are at a low level.
A commercially known majority gate provides an output high level signal when a majority of its inputs is at a high level, without indicating whether only some or all of its inputs are at a high level, and an output low signal when a majority of its inputs is at a low level.
It is well understood that a NOR function is obtained by inverting an OR function, a NAND function is obtained by inverting an AND function, and a minority function is obtained by inverting a majority function.
A multicolor semiconductor lamp comprising a plurality of light emitting diodes for emitting light of respectively different colors is disclosed in U.S. Pat. No. 3,875,456 issued on Apr. 1, 1975 to Tsuyoshi Kano et al. The light emitting diodes are closely adjacent and covered by a layer of light scattering material to provide an appearance of a single light source.
A majority logic gate, disclosed in U.S. Pat. No. 3,522,445 issued on Aug. 4, 1970 to Roy P. Foerster, utilizes precision resistors forming an input summation network and a differential amplifier for comparing the summation result with a threshold level.
A multicolor indicator, described in the article by William G. Ralphsnyder, entitled 2-color LED.times.3 bits=8 visual effects, published in EDN, Jul. 22, 1981, Volume 26, No. 14, pages 382 to 383, utilizes back-to-back connected red and green LEDs driven by a timer for providing eight visual effects. Since the LEDs are connected to conduct currents in opposite directions, it would be impossible to forwardly bias them simultaneously. The concept of back-to-back connected multicolor LEDs cannot be used in a three primary color multicolor device.